Coating asbestos fiber with aluminum sulfate prior to forming a cementasbestos slurry from the treated fibers to enhance the filtering characteristics of the slurries

ABSTRACT

ASBESTOS FIBER HAVING ALUMINUM SULFATE DEPOSITED ON ITS SURFACES AND ESPECIALLY WELL SUITED FOR FORMING FASTFILTERING ASBESTOS-CEMENT SLURRIES, THE PREPARATION OF SUCH FIBER, AND THE PRODUCTION OF WATER-LAID ASBESTOS-CEMENT PRODUCTS INVOLVING THE FORMATION OF THE FAST-FILTERING ASBESTOS-CEMENT SLURRIES UTILIZING THE ASBESTOS FIBER HAVING THE ALUMINUM SULFATE PREVIOUSLY DEPOSITED THEREON. SUCH ASBESTOS FIBER PRODUCT IS PREFERABLY DRY BUT CAN BE ONLY PARTIALLY DRY OR WET.

c. E. STIEFKEN 3,832,280 COATING ASBESTOS FIBER WITH ALUMINUM SULFATE PRIOR TO Aug. 27, 1974 FORMING A CEMENT-ASBESTOS SLURRY FROM THE TREATED FIBERS TO ENHANCE THE FILTERING CHARACTERISTICS or 'IHHSLURRIES Filed April 2:5. 197:

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o o o A g \GE WAZLQJ UZTJND UZOJHYIU llinlvf United States Patent 3,832,280 COATING ASBESTOS FIBER WITH ALUMINUM SULFATE PRIOR TO FORMING A CEMENT- ASBESTOS SLURRY FROM THE TREATED FIBERS TO ENHANCE THE FILTERING CHARACTERISTICS OF THE SLURRIES Charles Ernest Stiefken, Westfield, N.J., assignor to American Smelting and Refining Company, New York, N.Y.

Continuation-impart of abandoned application Ser. No. 226,218, Feb. 14, 1972, which is a division of Ser. No. 869,754, Oct. 27, 1969, now Patent No. 3,644,138. This application Apr. 23, 1973, Ser. No. 353,259

Int. Cl. D21h /18 US. Cl. 162-154 4 Clanns ABSTRACT OF THE DISCLOSURE Asbestos fiber having aluminum sulfate deposited on its surfaces and especially well suited for forming fastfiltering asbestos-cement slurries, the preparation of such fiber, and the production of water-laid asbestos-cement products involving the formation of the fast-filtering asbestos-cement slurries utilizing the asbestos fiber having the aluminum sulfate previously deposited thereon. Such asbestos fiber product is preferably dry but can be only partially dry or wet.

CROSS REFERENCES TO RELATED APPLICATIONS This is a continuation-in-part of application Ser. No. 226,218, filed Feb. 14, 1972, now abandoned, which in turn is a division of application Ser. No. 869,754, filed Oct. 27, 1969, now US. Pat. 3,644,138.

BACKGROUND OF THE INVENTION 1) Field of the Invention This invention relates to improving the filtration characteristics of asbestos and more particularly to a new and improved asbestos fiber product especially well suited for forming fast filtering asbestos-cement slurries, a method of preparing the new and improved fiber product, and to an improvement in the method of producing water-laid asbestos-cement products wherein a considerable faster filtration rate of the asbestos-cement slurry is achieved during the production.

(2) Description of the Prior Art Alkali metal silicates and phosphates have been deposited on asbestos fiber heretofor for improving filtration characteristics of the asbestos. High molecular weight polyacrylamides and naturally occuring guar gum have been added to asbestos-cement aqueous slurries by the asbestos-cement product producers, for improving the filtration rate of the asbestos-cement slurry. The use of the high molecular weight polyacrylamides and guar gum may result in clogging or plugging of the pores or openings of the felt, screen, perforated cylinder or other pourous means employed in forming the water-laid web of asbestos-cement. Papermakers alum, Al (SO.,)3-18H O, and a water-soluble salt of an organic carboxylic acid having or more carbons are also known in the prior art for addition to asbestos-cement slurries, as contrasted with deposition on the asbestos fiber prior to forming the 3,832,280 Patented Aug. 27, 1974 slurry, for forming fast draining slurries, and are disclosed and claimed in US. Pat. 3,014,835. Although the addition of the alum and the salt of the organic carboxylic acid having 10 or more carbons to the asbestoscement slurry is reported to give satisfactory results, there is room for improvement from the standpoint of speeding up the filtration rate of the asbestos-cement aqueous slurries inasmuch as the faster the draining or filtration rate, the greater the through-put and production rate of the asbestos-cement products. Hence it is readily seen that a considerable improvement in the filtration rate of asbestos-cement slurries should play an important role in the economics of the method of producing the asbestoscernent products. Further, the requirement of addition of additive materials to the asbestos-cement slurries by the asbestos-cement product manufacturer may put the manufacturer to an inconvenience, trouble and expense which he may not be desirous of having, and which would be obviated or eliminated by forming the slurry with asbestos fiber having the filtration-accelerating additive previously deposited thereon at the asbestos mill.

SUMMARY OF THE INVENTION In accordance with the present invention, I have found that an asbestos fiber product of considerably improved filtration characteristics is attained by applying to the asbestos fiber only, as contrasted with applying to an asbestor-cement slurry, a liquid solution of aluminum sulfate. After application of the aluminum sulfate solution onto the fiber the thus-treated fiber is collected for packaging or other disposition. Although the aluminum sulfate solution-treated fiber will usually be dried after application of such solution and before collecting the fiber, it is not essential to dry the treated fiber or, if the fiber is dried, to dry it completely. The drying of the thustreated fiber, if desired, can be effected by the application of external heat, or by simply allowing it to air dry or by other suitable means. The drying of the treated fiber serves to deposit aluminum sulfate solids on the fiber sulfaces, the deposited aluminum sulfate solids adhering to the fiber surfaces.

The product asbestos fiber of this invention is composed of the asbestos fiber having the aluminum sulfate deposited on surfaces of the fiber. The fiber is ordinarily composed of a plurality of asbestos fibers or numerous such fibers intertwined or clumped together in the usual manner characteristic of asbestos fiber. However, although it is unlikely, a single fiber having the aluminum sulfate deposited on its surface can, if desired, constitute the asbestos fiber of the product of this invention. The aluminum sulfate-treated asbestos fiber of this invention when dry will of course contain moisture in an amount which is in equilibrium with that of the surrounding air. As brought out supra, however, the aluminum sulfatetreated asbestos fiber of this invention can, if desired, be Wet, moist or only partially dry.

After application of the aluminum sulfate aqueous solution to the asbestos fiber and drying of the thus-treated fiber, the fiber can be fiberized, i.e. milled, if desired, to further liberate or free asbestos fiber which is agglomerated together by reason of the aqueous liquid of the aluminum sulfate solution. Such fiberizing of the aluminum sulfate-containing fiber does not adversely afiect the considerable improvement in filtration rate of the asbestos-cement slurry, and this was unexpected and surprising as it was felt that the mil-ling of the fiberizing would dislodge the adherent aluminum sulfate from the fiber surfaces to the extent of reducing materially faster filtration rate.

The asbestos fiber product of this invention is especially well suited for use in the production of water-laid cementasbestos products by reason of achieving a considerably improved water filtration rate. In the production of the water-laid cement-asbestos products an aqueous slurry is fomed of the cement and the asbestos fibers, and a waterlaid product is formed from the aqueous cement-asbestos fiber slurry by filtering or draining the water therefrom. The asbestos fiber and cement, such as Portland cement, are mixed together to form the cement-asbestos fiber slurry in a weight ratio of typically about 1:4 to 1:7 respectively. The utilization of the asbestos fiber product of this invention composed of the asbestos fiber having aluminum sulfate deposited on surfaces of the fiber per se as the fiber for forming the aqueous cement-asbestos fiber slurry, as contrasted with adding the aluminum sulfate to a previously formed aqueous cement-asbestos fiber slurry with the asbestos fiber free of the aluminum sulfate, attained a considerably faster rate of filtration of the water from the water-laid product.

The present invention is eminently well suited for improving the filtration characteristics of asbestos-cement slurries wherein the asbestos fiber is that normally found in the Province of Quebec, Canada, especially chrysotile fiber found in the Province. However the invention can also be practiced on other asbestos fiber as exemplified by amosite, cricidolite, anthrophyllite, tremolite and actino ite.

Any suitable aluminum sulfate is utilizable in accordance with this invention for deposition on the asbestos fiber. Thus the aluminum sulfate can be, for example, alum or papermakers alum, i.e. Al (SO -18H O, Al -(SO -14H O, Alg(SO ,-9H O, or Al2(SO The asbestos-cement water-laid products preparable in accordance with this invention are exemplified by asbestos-cement water-laid products preparable in accordance with this invention are exemplified by asbestos-cement sheets, boards, pipe, shingles, panels, clapboards, corrugated siding and roofing sheets, tubing, and other products including various special shapes and forms of the material.

The aluminum sulfate-treated asbestos fiber of this invention is utilizable in asbestos-cement compositions or products wherein the cement comprises a common hydraulic cement containing, for example Portland cement or a slag cement. The asbestos cement may also contain silica either as a filler or reactant, and the assorted fillers, pigments, etc., commonly utilized in the industry.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing is a fiow diagram for preparing the product asbestos fiber of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS tion deposited thereon is preferably dried prior to being collected. Less preferably such fiber can be collected in a partially dry or in a wet state, and the drying step can be omitted.

The spraying treatment results in a thin deposit or coating of the aluminum sulfate on the fiber. The deposit or coating can be a discontinuous and/ or continuous deposit or coating.

Although the amount of aluminum sulfate deposited or coated on the asbestos fiber can be varied over a wide range, it is preferred to deposit on the fiber an amount in the range of about 25-50 lbs. of the aluminum sulfate per ton of the fiber, more preferably about 30-40 lbs. thereof per ton, calculated as Al (SO With the preferred spray application, the aqueous solution of alumi num sulfate is of course a sprayable solution and will usually contain, by weight, about 1550% of the aluminum sulfate, preferably about 20-30% of the aluminum sulfate, calculated as Al (SO )3.

In the production of the cement-asbestos products, the aqueous slurry can be formed of hydraulic cement, for instance Portland cement, with or without silica, and the product asbestos fiber, for example product chrysotile asbestos fibers of this invention composed of a preferably dry asbestos fiber having the aluminum sulfate deposited on its surfaces. A water-laid web is then formed from the cement-asbestos fiber slurry by filtering off a major portion of the water of the slurry so that the fiber and cement are deposited to form a continuous solid wet sheet on a formanous surface such as, for example, a water absorbent felt, a moving screen, or a screen-covered perforated cylinder under a partial vacuum. The web thus formed is usually further consolidated and dewatered by applying a partial vacuum to suction rolls or felts or by pressure rolls as the web advances through the machine.

With reference to the drawing, the oversize asbestos fiber from the fiber screens is pneumatically fed through tangentially disposed inlet 5 into classifier cyclone 6 wherein the asbestos fiber is cyclonically separated from the dust. The separated fiber is withdrawn from cyclone 6 through outlet 7, with the dust being withdrawn from the cyclone through outlet 8. The fiber is then conveyed through screw conveyor 9 having an open top. An aluminum sulfate aqueous solution is sprayed onto the asbestos fiber being conveyed through conveyor 9 by one or more spray nozzle 10. The aluminum sulfate solution is mixed with the fiber by the subsequent movement of the treated fiber through the screw conveyor.

The thus-treated fiber is then dried by radiant heat applied from a battery of drying lamps 11, such as infrared lamps, mounted above the discharge end of the open top conveyor 9 and in closely spaced relationship thereto. Alternatively any suitable or conventional drying means or system can be utilizable in place of the drying lamps 11. The dried fiber having the aluminum deposited on and adhered to its surfaces passes from the discharge end 12 of screw conveyor 10 into fiber bin 13(The fiber is withdrawn from bin 13 through outlet 14, and a minor or major portion of the fiber is returned to bin 13 via bucket conveyor 15 for purpose of blending. Alternatively the remaining fiber, or all fiber when no recycling of fiber to bin 13 is employed, from bin 13 is passed by conveyor 16 to the preliminary compression screw unit 17 wherein the fiber is compressed to a limited or relatively small extent. From preliminary compression unit 17 the fiber having the aluminum sulfate as sole filter aid deposited on and adhered to its surfaces is passed via conveyor 18 to the compression unit wherein it is compressed to the desired final extent, after which the compressed fiber is packaged.

The test data of Table I which follows, shows the improvement in filtration attained by spraying the asbestos fiber with the aluminum sulfate as potential filter aid or reagent over adding the potential filter aid directly to the asbestos-cement slurry. In carrying out the tests, in applying the potential filter aid to the fiber, 4T3 asbestos fiber obtained from the Black Lake region of Quebec Province, Canada was sprayed with an aqueous solution of the potential fiber aid, dried for thirty minutes at 212 F. and fiberized by ball milling and double-pass disintegration. The thus-treated fiber was mixed with Portland cement and saturated lime-gypsum water to form an asbestoscement slurry for the filtration tests. In the tests wherein the potential filter aid was added to the slurry of asbestos to separate the water from the asbestos-cement. The test results are set forth hereafter in Table II:

and cement, the addition of the potential filter aid to the TABLE H slurry was made by mixing together the asbestos fiber, celfiltration ment, and saturated lime-gypsum water, then adding the 5 Fiber 313]? w tig tii i ri titpotential filter aid and/ or reagent, and mixing further. In (ca) (ca) c (p all tests the results of which are reported in Tables I and 0 0 68 Control II which follow, the same ratio of asbestos fiber (treated t8 8 g? g and untreated) of Portland cement was used in preparing 10 10 2O 52 5 each asbestos-cement slurry, viz. grams of asbestos fiber 10 30 53 22 to 85 grams of cement. 650 cc. of saturated lime-gypsum 5R3 O 0 90 Control water was also used in preparing each asbestos-cement 10 10 71 10 20 69 23 slurry of such tests.

TABLE I Reagent Filtration Filtration Added to improve- Sprayed onto asbestos-cement Time Atime ment Asbestos fiber fiber slurry (seo.) (sec) (percent) 4T3 SE-1115--- 55 0 Control 47 8 15 54 1 2 56 0 56 0 61 0 58 0 Na2CO3 55 0 0 A1Cla-l-Na2COs 56 0 4T3 SE-8754 60 0] Control 4T3 SE-8754 Alz(SO4)3 45 5 4T3 SIS-8754 Alz(SO4)a 59 1 2 4T3 SE-1l15 54 0 Control 4T3 SIB-1115 Al2(SOr)3 42 12; 22 4T3 SIB-1115 masons 51 3 a 4T3 SE-1115 Na oleate 59 0 In the foregoing Table I, the designations SE-1115 and 1 l i SE-8754 mean two different samples of the same grade 1 In a method f Producing a waterqaid asbestosof fiber. As shown by the test data of Table I the applica- Cement product b forming a t -l id od t from tion of the aluminum sulfate to the asbestos fiber increased h aqueous slurry b filt i h Water h f the the rate of filtration of the ultimate asbestos-cement slurry improvement h b an increased water filt tio r te y about 15-25% Whereas y an about lhotease is attained which comprises utilizing as the asbestos fiber in the filtration rate was obtained y adding ahlmlhhm for forming the slurry an asbestos fiber having aluminum sulfate to the slurry of asbestos and cement. Also as shown lf t as sole filt aid previously deposited on y the test data of Table the application to the ashostos faces of the fiber in an effective amount sufficient to fiber of the following Potential filter aids resulted In no result in the increased water filtration rate, the aluminum increase in the filtration rate of the ultimate asbestos-ce lf te-tr ted asbestos fib having b prepared by moht y aluminum ohlorido P Sodium Carbonate, applying to only discrete asbestos fiber a liquid aqueous di Carbonate aloho- The application o ahlmlhhm 5 solution consisting essentially of aluminum sulfate, and chloride alone to the asbest s fi r resulted 1 y a 2% collecting the thus-treated fiber having the aluminum sulincrease in the filtration rate of the ultimate asbestosfate as l filter id d i d h cement slurry. 2. The method of claim 1 wherein the aluminum The following test data of Table II {1150 CVIdGIICGS the sulfate is depgsited on the fiber urfaces by spraying a, considerable improvement in the filtration rate of asbesli id l ti f th l i lf t o th fib tos-cement aqueous slurries provided by utilizing therem 3, Th th d f l i 2 h i th l i sulas the asbestos fiber that having ahlmlhhl'fl Sulfate pr fate is deposited on the fiber in amount in the range of viously deposited on the fiber surfaces as compared with about 25-50 lbs. of the aluminum sulfate, calculated as the use in the slurry of asbestos fiber not having aluminum AI (SO per t of fib sulfate deposited thereon. In the tests, commercial con- H 4. The method of claim 1 wherein the fiber is chrysotile centrated aqueous liquid alum solution was sprayed on M asbestos fiber. 4T3 and 5R3 asbestos fiber at concentrations equivalent References Cited to 7.9 gallons of the commercial liquid per ton of fiber. Such fiber was obtained from ore mined in the vicinity of UNITED STATES PATENTS Black Lake, Province of Quebec, Canada. Various dilu- 3,535,150 10/1970 Llhsott AF tions of the commercial concentrated liquid alum with dis- 350142835 12/1961 Folgloy, tilled water were also sprayed on separate and similar 2,563,023 9/1951 o y -15 quantities of the 4T3 and 5R3 asbestos-fiber. The thus- $532,460 6/1971 Llpsett 117126 AF treated fiber was then dried for 15 minutes at 200 F. followed by fiberizing by ball milling for 60 minutes and 5 LEON BASHORE Pnmary Exammer double-pass disintegrating. Asbestos-cement aqueous slurries were then prepared utilizing the fiberized and opened fibers containing the alum, and filtration tests were run on the slurries to determine the filtration times required W. F. SMITH, Assistant Examiner US. Cl. X.R. 162-l82, 183

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No .3 ,832 280 Dated August 27 1974 lnventor(s) l E Stiefken It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 59, "pourous should read porous Column 3 line 3 "the" should be inserted after "reducing" and before "materially"; line 10, "fomed" should read formed line 31, "cricidolite" should read crocidolite lines 39-41, the language asbestos-cement water-laid products preparable in accordance with this invention are exemplified by" should. be deleted. Column 6, line 34, after "forming" and before a" the language an aqueous slurry of the cement and asbestos fiber, and forming should be inserted.

Signed and Sealed this tenth Day Of February 1976 C [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting ff Commissioner oj'iarents and Trademarks 

